Biomedical subjects

Dick M Goedhart

Publications and source records attributed to Dick M Goedhart.

7 recordsLinked to original sources

PubMed2006

Evaluation of morphology discrimination for ventricular tachycardia diagnosis in implantable cardioverter-defibrillators.

BACKGROUND: To reduce inappropriate therapy from implantable cardioverter-defibrillators (ICDs), electrogram morphology discrimination has been developed to improve arrhythmia discrimination without compromising device safety. OBJECTIVES: The purpose of this study was to determine the accuracy of the morphology discrimination algorithm for detecting ventricular tachycardia (VT). METHODS: Stored electrograms of 795 tachyarrhythmias from 106 patients with a St. Jude Medical ICD (51 single-chamber and 55 dual-chamber) were analyzed by the investigators. The data were analyzed for morphology discrimination alone, sudden onset and stability, and morphology discrimination in combination with sudden onset and stability. Data were corrected for multiple episodes within a patient with the generalized estimating equation method. RESULTS: Using the nominal template match of 60%, morphology discrimination alone provided sensitivity and specificity of 78% and 95% for single-chamber ICDs and 63% and 92% for dual-chamber ICDs, respectively. Based on the receiver operator characteristic curve, the optimal-match percent threshold was 80% to 85% but at the expense of specificity. Morphology discrimination combined with sudden onset and stability increased sensitivity to 98% with specificity of 86% in single-chamber devices. In dual-chamber devices, the loss in sensitivity is compensated by rate branch analysis, yielding a sensitivity of 98%. CONCLUSION: Arrhythmia discrimination based on electrogram morphology has the potential to reject atrial tachyarrhythmias. However, there is a risk for underdetection of ventricular tachyarrhythmias if arrhythmia discrimination is primarily based on morphology. To guarantee patient safety in single-chamber devices, the morphology discrimination algorithm must be programmed in combination with established detection algorithms. In dual-chamber devices, loss of sensitivity is compensated by the V > A rate branch.

Algorithms↗

PubMed2006

Treatment benefit by perindopril in patients with stable coronary artery disease at different levels of risk.

AIMS: Patients with stable coronary artery disease (CAD) are at increased risk. Estimation of individual risk is difficult. We developed a cardiovascular risk model based on the EUROPA study population and investigated whether benefit of long-term administration of the angiotensin-converting enzyme (ACE)-inhibitor perindopril was modified by risk level. METHODS AND RESULTS: A total of 12 218 patients with stable CAD were treated with 8 mg perindopril or placebo. Baseline patient characteristics were assessed for association with 1091 cardiovascular deaths or non-fatal myocardial infarction (MI). Risk factors were age over 65 years, male gender [hazard ratio (HR) 1.2], previous MI (HR 1.5), previous stroke and/or peripheral vascular disease (HR 1.7), diabetes, smoking, angina (all HR 1.5), and high serum cholesterol and systolic blood pressure. Treatment benefit by perindopril was consistent among high, intermediate, and low risk patients (HRs 0.88, 0.68, and 0.83, respectively). Risk reduction was thus not modified by absolute risk level. CONCLUSION: Risk factors such as age, male gender, smoking, total cholesterol, and blood pressure continue to play an important role once clinical sequellae of coronary heart disease have developed. Patients at moderate-to-high risk because of uncontrolled risk factors and those with other indications for ACE-inhibitors have the most to gain from ACE-inhibition.

Adult↗

PubMed2006

Relevant and redundant lung function parameters in discriminating asthma from COPD.

A relevant set of lung function parameters, derived from spirometry, flow-volume curves, diffusion capacity and bodyplethysmography, to discriminate asthma from COPD was established via logistic regression analysis. All new patients, referred to the outpatient clinic and later defined as asthma or COPD, underwent extensive lung function testing with reversibility testing. Logistic regression was used to calculate the probability to be a COPD or asthma patient. Selection of relevant parameters was done via 1] forward-, 2] backward-, 3] stepwise selection and 4] the best score method. All four methods were supplemented by bootstrapping to obtain a validated selection and estimation of the logistic regression parameters. The area under the ROC curve (mean+/-sd) for respectively the forward, backward, stepwise and best score selection method is 0.9348+/-0.0115, 0.9346+/-0.0115, 0.9348+/-0.0115 and 0.9296+/-0.0121. The TLCO, VA and the postdilator MEF50, VC and PEF were selected as the most relevant parameters in discriminating asthma from COPD: they appeared most often as relevant discriminators in 500 bootstrapped samples: TLco was present in all bootstrapped samples and VA, postdilator MEF50, VC and PEF in resp. 70.8%, 46.2%, 42.8% and 36.8%. Bodyplethysmography derived parameters turned out to be of limited value. Diffusion capacity testing and spirometry/flow-volume curve after administration of bronchodilators are the methods of choicewhen having to chose between asthma or COPD.

Adult↗

PubMed2005

Discriminating asthma and COPD based on bronchodilator data: an improvement of the methods.

The degree of bronchodilation is usually expressed as a percentage of the predicted or baseline value. It has been shown that the relation between pre- and post-dilation lung function values is not adequately described by this approach: the sensitivity/specificity in separating asthmatics from cases of chronic obstructive pulmonary disease (COPD) could be improved. The alternative method we investigate is based on a logistic regression approach incorporating pre- and post-dilation lung function, age, sex and height. The discriminatory power of forced expiratory volume in one second (FEV1) increase as a percentage of the predicted or baseline FEV1 is compared to our approach using two databases containing bronchodilator data and diagnoses (asthma, chronic bronchitis or emphysema, the latter two grouped as (OPD). The increase as a percentage of the predicted or baseline approach and our alternative method show areas under the receiver operator curve (ROC) (males/females) of 0.552/0.629, 0.523/0.550 and 0.867/0.879 in one database. In the other database the same trend is present although less obvious: 0.628/0.730, 0.592/0.737 and 0.709/0.749. This increase in discriminatory power is obtained in the optimal use of all available information, especially age, which is not used in the increase of the predicted/baseline FEV1 rule.

Adult↗

PubMed2004

Prevention of inappropriate therapy in implantable cardioverter-defibrillators: results of a prospective, randomized study of tachyarrhythmia detection algorithms.

OBJECTIVES: The purpose of this randomized study was to investigate the performance of single- and dual-chamber tachyarrhythmia detection algorithms. BACKGROUND: A proposed benefit of dual-chamber implantable cardioverter-defibrillators (ICDs) is improved specificity of tachyarrhythmia detection. METHODS: All ICD candidates received a dual-chamber ICD and were randomized to programmed single- or dual-chamber detection. Of 60 patients (47 male, age 58 +/- 14 years, left ventricular ejection fraction 30%), 29 had single-chamber and 31 had dual-chamber settings. The detection results were corrected for multiple episodes within a patient with the generalized estimating equations method. RESULTS: A total of 653 spontaneous arrhythmia episodes (39 patients) were classified by the investigators; 391 episodes were ventricular tachyarrhythmia (32 patients). All episodes of ventricular tachyarrhythmias were appropriately detected in both settings. In 25 patients, 262 episodes of atrial tachyarrhythmias were recorded. Detection was inappropriate for 109 atrial tachyarrhythmia episodes (42%, 18 patients). Rejection of atrial tachyarrhythmias was not significantly different between both groups (p = 0.55). Episodes of atrial flutter/tachycardia were significantly more misclassified (p = 0.001). Overall, no significant difference in tachyarrhythmia detection (atrial and ventricular) between both settings was demonstrated (p = 0.77). CONCLUSIONS: The applied detection criteria in dual-chamber devices do not offer benefits in the rejection of atrial tachyarrhythmias. Discrimination of atrial tachyarrhythmias with a stable atrioventricular relationship remains a challenge.

Adult↗

PubMed2004

Analyzing bronchodilation with emphasis on disease type, age and sex.

In the literature, different statistical methods to evaluate bronchodilator studies are used. These approaches are all based on the absence of residual heterogeneity and on baseline independency of the parameter under analysis. A database containing the lung function values of newly referred patients was used to assess these assumptions as function of the underlying diagnosis (asthma, bronchitis and emphysema) and to chart the characteristics of analysis of covariance, which (partly) deals with these drawbacks. Bronchodilator data of 709 asthmatics, 522 bronchitic and 126 emphysema patients were used. It was shown that, in asthma, for almost all lung function parameters, bronchodilation was indeed dependent on baseline values, which was less strong in bronchitis and even weaker in emphysema. A negative effect of age on bronchodilation was found, which is strong in asthma and almost absent in emphysema, rendering the use of bronchodilation as a diagnostic tool less useful. The conclusion is that analysis of covariance is a good way to evaluate bronchodilation studies in obstructive lung disease, particularly in asthma. For bronchitic or emphysema patients, difference-based approaches may suffice. The assumptions underlying the other methods were not met.

Adult↗

PubMed2002

Selecting the best method to evaluate bronchodilation when analysing bronchodilator studies.

Changes in lung function (that is, FEV(1)) are commonly expressed as a percentage of the predicted value. The question is whether this parameter is best suited for statistical analysis. A total of 2199 bronchodilation tests were selected and pre- and post-dilator FEV(1), age, height and sex extracted. Predicted FEV(1) values, the difference between pre- and post-dilator FEV(1) and the change as percentage of predicted or baseline FEV(1) were calculated. The latter parameters were subjected to analysis of variance and pre- and post-dilator FEV(1) to analysis of covariance. The statistical power of these four approaches and the residual structure were used to select the best approach. Analysis of variance of the change as percentage of predicted and covariance analysis of pre- and post-dilator FEV(1) offers the best performance. The residuals of the analysis of variance showed a funnel shaped structure. The latter causes residual heterogeneity, resulting in a loss of power and deviations between the actual and nominal alpha-level. This is not taken into account when calculating sample sizes using the standard equations, which implicitly assume lack of these problems. Analysis of covariance does not suffer from these problems. The best way to evaluate bronchodilation in trials is to use analysis of covariance.

Age Factors↗